Systems and methods for coupling a semiconductor device of an automation device to a heat sink

ABSTRACT

A system includes a heat sink, a semiconductor device, a layer of thermal interface material (TIM) disposed between the heat sink and the semiconductor device, and a fastener system that couples the semiconductor device, the layer of TIM, and the heat sink together. The TIM may facilitate dissipation of heat generated by the semiconductor device via the heat sink during operation of the semiconductor device. The fastener system includes a first Belleville-type washer configured to cooperate with the TIM, which flows when heated beyond a threshold temperature, to maintain a substantially constant coupling force between the semiconductor device and the heat sink during operation of the semiconductor device.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and benefit of U.S. application Ser.No. 14/147,285, entitled “SYSTEMS AND METHODS FOR COUPLING ASEMICONDUCTOR DEVICE OF AN AUTOMATION DEVICE TO A HEAT SINK,” filed Jan.3, 2014, which is herein incorporated by reference in its entirety.

BACKGROUND

Embodiments of the present disclosure relate generally to systems andmethods for improving a manufacturing process used for assemblingindustrial automation devices. More specifically, the present disclosureis generally related to improved systems and methods for attaching asemiconductor device to a heat sink during the manufacturing process ofan industrial automation device.

Industrial automation systems may employ various types of electronicdevices such as an alternating current (AC) drive, a motor, a robot, orthe like to perform various industrial processes. Generally, theseelectronic devices use semiconductor devices to control the power beingused by the respective devices. As such, part of the manufacturingprocess of an industrial automation device includes coupling asemiconductor device to a heat sink, such that the semiconductor devicecan operate without overheating. It is generally desirable for thesemiconductor device to be coupled to the heat sink with a particularforce to provide stable coupling and to facilitate efficient heattransfer between the semiconductor device and the heat sink.Accordingly, improved systems and methods for manufacturing theseelectronic devices and providing couplings between the respectivedevices and heat sinks are desirable.

BRIEF DESCRIPTION

In one embodiment, a system includes a heat sink, a semiconductordevice, and a layer of thermal interface material (TIM) disposed betweenthe heat sink and the semiconductor device. The TIM may facilitatedissipation of heat generated by the semiconductor device via the heatsink. The system also includes a fastener system that couples thesemiconductor device to the heat sink about the layer of TIM. The systemalso includes one or more washers of the fastener system that maintain acoupling force between the semiconductor device and the heat sink afterthe TIM flows.

In another embodiment, a non-transitory computer-readable mediumincludes computer-executable instructions that cause thecomputer-readable medium to receive a first set of properties associatedwith a first type of washer of one or more washers that maintain acoupling force between a heat sink and a semiconductor device after athermal interface material (TIM) disposed between the semiconductordevice and the heat sink flows. The computer-readable medium may thendetermine an expected deflection of the one or more washers after thefastener is torqued to a torque value based on the first set ofproperties and an expected axial force between the heat sink and thesemiconductor device. The computer-readable medium may then determine anexpected residual force between the heat sink and the semiconductordevice after the TIM between the heat sink and the semiconductor deviceflows, such that the expected residual force is determined based on theexpected deflection and an expected change in thickness of the TIM afterthe TIM flows. The computer-readable medium may then determine that thefirst type of washer will adequately maintain a minimum force betweenthe heat sink and the semiconductor device after the TIM flows when theexpected residual force is greater than a value.

In yet another embodiment, an industrial automation drive may include aheat sink-semiconductor assembly. The heat sink-semiconductor assemblymay include a thermal interface material (TIM) disposed between asemiconductor device and a heat sink. The semiconductor device may beused to convert an alternating current (AC) voltage into a directcurrent (DC) voltage or convert the DC voltage into a controllable ACvoltage. The heat sink-semiconductor assembly may also include afastener that couples the semiconductor device to the heat sink and oneor more washers that may be inserted into the fastener. Here, thewashers may maintain a force between the semiconductor device and theheat sink after the TIM flows.

DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 illustrates a perspective view of an example heatsink-semiconductor assembly, in accordance with embodiments presentedherein;

FIG. 2 illustrates a block diagram of the heat sink-semiconductorassembly of FIG. 1, in accordance with embodiments presented herein;

FIG. 3A illustrates a top view of a fastener system that may be employedin the heat sink-semiconductor assembly of FIG. 1, in accordance withembodiments presented herein;

FIG. 3B illustrates a cross-sectional view taken along line A-A of thefastener system of FIG. 3A, in accordance with embodiments presentedherein;

FIG. 3C illustrates a side view of the fastener system of FIG. 3A, inaccordance with embodiments presented herein;

FIG. 3D illustrates a perspective view of the fastener system of FIG.3A, in accordance with embodiments presented herein;

FIG. 4A illustrates a top view of a washer that may be employed in thefastener system of FIGS. 3A-3D;

FIG. 4B illustrates a side view of a washer that may be employed in thefastener system of FIGS. 3A-3D;

FIG. 4C illustrates a perspective view of a washer that may be employedin the fastener system of FIGS. 3A-3D; and

FIG. 5 illustrates a flow chart of a method for identifying a washerthat may be employed in the fastener system of FIGS. 3A-3D.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

Embodiments of the present disclosure are generally directed towardsimproved systems and methods for manufacturing industrial automationdevices. Industrial automation devices such as drives, motor starters,rectifiers, and the like may use semiconductor devices to control powerused or output by the respective devices. Semiconductor devices, such asinsulated-gate bipolar transistors (IGBTs), may be used by industrialautomation devices to accommodate efficient and fast switching to altervoltage waveforms received by the devices. As the semiconductor deviceswitches, however, the semiconductor device may generate heat that mayreduce the life of the semiconductor device or the industrial automationdevice in which the semiconductor device is located. As such, asemiconductor device may be coupled to a heat sink, which may dissipatethe heat generated by the semiconductor device away from thesemiconductor device, the industrial automation device, or both.

For example, the industrial automation device may be an electric drivethat may include a rectifier circuit, such as a Diode Front End (DFE)rectifier an Active Front End (AFE) rectifier that may convertalternating current (AC) voltage into a direct current (DC) voltage. Theelectric drive may also include an inverter circuit that may convert theDC voltage into a controllable AC voltage that may be provided to amotor that may be coupled to a load. In this example, semiconductordevices may be used in the rectifier circuit and/or the inverter circuitto effectively convert the AC voltage into the DC voltage and to convertthe DC voltage into the controllable AC voltage. That is, thesemiconductor devices may rapidly switch off and on to generate a DCvoltage waveform and a controllable AC voltage waveform. However, asmentioned above, as the semiconductor device switches, the semiconductordevices may generate heat that should be dissipated away from thesemiconductor device. As such, a heat sink may be coupled to eachsemiconductor device to dissipate heat away from the semiconductordevice.

In order to provide a stable attachment and efficient heat transfer viathe heat sink, it may be desirable to couple the semiconductor deviceand the heat sink together with a level of force within a certain range.Additionally, to further enable heat to transfer more efficiently fromthe semiconductor device to the heat sink, a thermal interface material(TIM) may be applied to a surface of the heat sink and/or to a surfaceof the semiconductor device where the heat sink and the semiconductordevice interface or physically contact each other when coupled together.The TIM may fill in gaps that would otherwise exist at such interfacessuch that better heat transfer occurs. A fastener coupling thesemiconductor device and heat sink will generally apply force to the TIMpositioned between the coupled features. However, it is now recognizedthat due to heat generated by the semiconductor device while operating,the TIM between the semiconductor and the heat sink may melt or flow. Asa result, a portion of the force used to couple the semiconductor deviceand the heat sink may be lost.

Generally, the heat sink and the semiconductor device may be coupledtogether using a fastener system. As such, the thermal transferproperties of the TIM may depend on a pressure or coupling force betweenthe heat sink and the semiconductor device when coupled together via thefastener system. The fastener system may be torqued to a particulartorque value, such that a pressure or coupling force between the coupledheat sink and semiconductor device is sufficient to enable the TIM toeffectively transfer heat from the semiconductor device to the heatsink.

When an industrial automation device is placed in service, the devicemay experience a burn-in process. That is, when the industrialautomation device is initially placed in service, heat generated by thesemiconductor device in the industrial automation device may cause theTIM to melt or flow. During this burn-in process, the TIM may changefrom a solid state to a semi-liquid state. When the TIM is in thesemi-liquid state, the TIM may spread across the surface of the heatsink and fill in gaps that may exist on the surfaces of the heat sinkand the semiconductor device. After the initial change from the solidstate to the semi-liquid state, the TIM may change again into the solidstate. At this point, the thickness of the TIM may have decreased due tothe changes of state by the TIM and due to the TIM filling in the gapson the surfaces of the heat sink and the semiconductor device. As aresult of this thickness change, the pressure or coupling force betweenthe coupled heat sink and semiconductor device may also decrease,thereby reducing the ability of the TIM to transfer heat to the heatsink efficiently.

To compensate for this loss in pressure, the presently disclosedmanufacturing process may include coupling the heat sink to thesemiconductor device using the TIM, torquing a fastener system used tocouple the heat sink to the semiconductor device to a particular torquevalue, heating the coupled heat sink-semiconductor assembly in anindustrial oven, and then re-torqueing the coupled heatsink-semiconductor assembly back to the particular torque value. In thismanner, the manufacturing process may compensate for the loss ofpressure or coupling force between the heat sink-semiconductor assemblydue to the TIM melting or flowing by re-torqueing the heatsink-semiconductor assembly after the TIM has been heated. After the TIMhas melted or flowed once, the gaps of the surfaces of the heat sink andthe semiconductor device may be filled, and any future melting orflowing of the TIM may be limited. That is, after the TIM is heatedonce, the heat sink-semiconductor assembly may not experience anysignificant loss in pressure or coupling force between the coupled heatsink and semiconductor device.

Although the method described above may compensate for the loss ofpressure or coupling force between the heat sink and semiconductordevice, the use of an oven in the manufacturing process may involvestoring and operating a large heating device at a manufacturingfacility. Moreover, the process of re-torqueing the heatsink-semiconductor assembly may be an inefficient use of manufacturingtime (e.g., man hours). In addition to the time and cost issuesdiscussed above, the above manufacturing process may include a risk offailing to re-torque certain fasteners after the TIM flows, a risk ofdamaging hardware during the re-torqueing process, a delivery delayassociated with the re-torqueing process, and added costs formaintaining and operating an industrial oven.

Keeping the foregoing in mind, in one embodiment, each of the fastenersused to couple the heat sink to the semiconductor device may include aseries of Belleville-style washers, such that each adjacentBelleville-style washer in the series may be arranged in a reverseposition. That is, each adjacent Belleville-style washer in the seriesmay be arranged in opposite directions. As a result, theBelleville-style washers may act as springs limiting the loss ofpressure or coupling force between the heat sink and the semiconductordevice after the semiconductor device moves and/or the thickness of theTIM decreases during the burn-in process. By limiting the loss ofpressure or coupling force between the heat sink and the semiconductordevice during the burn-in process, the manufacturing process for theindustrial automation device may no longer involve heating the heatsink-semiconductor assembly using an oven and re-torqueing the heatsink-semiconductor assembly.

By way of introduction, FIG. 1 illustrates a perspective view of anexample heat sink-semiconductor assembly 10 that may be employed invarious types of industrial automation devices. The heatsink-semiconductor assembly 10 may include a heat sink 12 and asemiconductor device 14. The heat sink 12 may be a passive heatexchanger that cools the semiconductor device 14 by dissipating heatgenerated by the semiconductor device 14 away from the semiconductordevice 14. The semiconductor device 14 may include any type ofsemiconductor switch such as diodes, bipolar transistors, field-effecttransistors, insulated-gate bipolar transistors (IGBT), thyristors, andthe like, that may be coupled to a heat sink.

In certain embodiments, the semiconductor device 14 may be coupled tothe heat sink 12 using fastener system 16. The fastener system 16 mayinclude any type of component that may be used to couple two objects(e.g., semiconductor 14 and heat sink 12) together. As such, thefastener system 16, for example, may include screws, nuts, clamps,bolts, or the like.

Before coupling the semiconductor device 14 to the heat sink 12, athermal interface material (TIM) may be applied to surfaces 18 of thesemiconductor device 14 and the heat sink 12 where the semiconductordevice 14 and the heat sink 12 may physically contact each other whencoupled together. FIG. 2, for example, depicts a block diagram view 15of the heat sink-semiconductor assembly 10 illustrating a position ofthe TIM 19 with respect to the heat sink 12 and the semiconductor device14.

The TIM 19 may be a viscous fluid substance that may increase a thermalconductivity of the interface of the heat sink 12 by filling microscopicair-gaps on the surface 18 of the heat sink 12 or the semiconductordevice 14. That is, since the surfaces 18 of the heat sink 12 and thesemiconductor device 14 may be imperfectly flat or smooth, the TIM 19may fill in those imperfections when the TIM 19 melts. As a result, theTIM 19 may enable the heat sink 12 to more efficiently dissipate theheat generated by the semiconductor device 14.

In order to ensure that heat is effectively dissipated by the heat sink12 and the TIM 19, a particular pressure or axial force between the heatsink 12 and the semiconductor device 14 should be maintained. As such,the particular pressure between the heat sink 12 and the semiconductordevice 14 may be obtained by torquing the fastener system 16 to aparticular torque value when coupling the semiconductor device 14 to theheat sink 12. The torque value may be specified by the supplier of thesemiconductor device 14 as a minimum mounting torque value. Generally,the fastener system 16 should maintain the minimum mounting torque valueor a percentage of the minimum mounting torque value after the burn-inprocess to ensure that the heat from the semiconductor device 14effectively dissipates via the heat sink 12.

In one embodiment, each fastener system 16 may include one or morewashers that may be inserted on a fastener used to couple thesemiconductor device 14 to the heat sink 12. As such, the washers maylimit the loss of pressure or coupling force between the semiconductordevice 14 and the heat sink 12 after the burn-in process. FIG. 3A, FIG.3B, FIG. 3C, and FIG. 3D, for example, depict a top view 20, across-sectional view 22, a side view 30, and a perspective view 40 of awasher-fastener system 22 that may be employed when coupling thesemiconductor device 14 to the heat sink 12.

Referring now to FIGS. 3A-3D, the fastener system 16 may include afastener 23 inserted through one or more washers 24 and a flat washer26. The washers 24 may be Belleville-type washers, which may also beknown as a coned-disc spring, a conical spring washer, a disc spring, aBelleville spring, or a cupped spring washer. In one embodiment, thewashers 24 may have a frusto-conical shape that may provide each washer24 with a spring characteristic.

As shown in FIGS. 3B-3D, the washers 24 may be placed in series witheach other to provide a certain amount of force between the heat sink 12and the semiconductor device 14. In one embodiment, the fastener 23 mayinclude a thread lock patch, as shown with the dashed lines in FIGS.3B-3D. Although FIGS. 3B-3D illustrate three washers 24 on the fastener23, it should be noted that the systems and techniques described hereinare not limited to using three washers 24. Instead, it should beunderstood that the systems and techniques it should also be understoodthat the systems and techniques described herein may be employed usingany number of washers 24. Additionally, it should be noted that thesystems and techniques described herein may be employed using a varietyof different sized fasteners 23, washers 24, and flat washers 26.

Various views of an example washer 24 are depicted in FIGS. 4A-4C. Asshown in a top view 50, a side view 60, and a perspective view 70 ofFIGS. 4A, 4B, and 4C, respectively, the washer 24 may have a first sidehaving a diameter 52 and a second side having a diameter 54. Thediameter 52 may be positioned at the apex of the frusto-conical shapedwasher 24 and the diameter 54 may be positioned at the base of thefrusto-conical shaped washer 24. Generally, the diameter 52 may be lessthan the diameter 54.

Keeping this in mind and referring back to FIGS. 3A-3D, in oneembodiment, a first washer 24 placed on the fastener 23 (i.e., thewasher 24 closest to a head 25 of the fastener 23) may be inserted intothe fastener 23 in any direction. That is, the first washer 24 may beplaced against the head 25 of the fastener 23, such that a first side ofthe washer 24 having a larger diameter (i.e., diameter 54) may be placedagainst the head 25 of the fastener 23. Alternatively, a second side ofthe washer 24 having a smaller diameter (i.e., diameter 52) may beplaced against the head 25 of the fastener 23. In either case, anywasher 24 following the first washer 24 may be inserted in an oppositedirection as the immediately preceding washer 24. For example, if thefirst washer 24 placed against the head 25 of the fastener 23 isarranged such that the side having the larger diameter rests against thehead 25 of the fastener 23, then a second washer 24, immediatelyfollowing the first washer 24, may be placed such that the side of thesecond washer 24 having the smaller diameter (i.e., diameter 52) may beplaced against the side of the first washer 24 having the smallerdiameter (i.e., diameter 52).

After the series of washers 24 have been inserted on the fastener 23 inan alternating manner, a flat washer 26 may be placed at the end of theseries of washers 24. The flat washer 26 may distribute a force appliedby the washers 24 on the head 25 of the fastener 23 and against the heatsink 12 and/or the semiconductor device 14. Although the foregoingdiscussion of the fastener system 16 is described with reference to thehead 25 of the fastener 23, it should be noted that in embodiments wherethe fastener 23 is a clamp, for example, the washer 24 may be placeadjacent to the body of the clamp.

As discussed above, the fastener 23 may be used to couple thesemiconductor device 14 to the heat sink 12 and to apply a particularpressure or coupling force between the semiconductor device 14 and theheat sink 12. However, in order to compensate for the loss of pressureor coupling force due to the TIM 19 flow during the oven heating portionof the manufacturing process or after the burn-in process of theindustrial automation device having the heat sink-semiconductor assembly10, the washers 24 may provide a spring force or pressure between thesemiconductor device 14 and the heat sink 12 after the TIM 19 flows.That is, after the TIM 19 flows and the thickness of the TIM 19decreases, the initial pressure between the heat sink-semiconductorassembly 10 may decrease. However, this loss of pressure may cause thespring attributes of the washers 24 to expand and compensate for atleast a portion of the total pressure loss.

Generally, the type of washer 24 and the number of the washers 24 usedto provide a sufficient amount of force or pressure between the heatsink 12 and the semiconductor device 14 may be determined based on asize of the fastener 23, an amount of torque being applied to thefastener 23, and an amount of expected deflection between the heat sink12 and the semiconductor device 14 due to the TIM 19 flow. Keeping thisin mind, FIG. 5 illustrates a flow chart of a method 80 for determininga type of washer 24 and a number of washers 24 that may be employed inthe fastener system 16.

In one embodiment, the method 80 may be performed by a computing devicethat may include a processor, a memory, a storage, and the like. Theprocessor may be any type of computer processor or microprocessorcapable of executing computer-executable code. The memory and thestorage may be any suitable articles of manufacture that can serve asmedia to store processor-executable code. These articles of manufacturemay represent computer-readable media (i.e., any suitable form of memoryor storage) that may store the processor-executable code used by theprocessor to perform the presently disclosed techniques. Thecomputer-readable media is tangible and non-transitory, which merelymeans that the computer-readable media is not a signal.

Referring now to FIG. 5, at block 82, the computing device may receivedata related to one or more properties of a type of a washer 24 that maybe used with the fastener 23, as described above. The properties mayinclude a maximum washer compression force and a maximum washerdeflection associated with the washer 24. These properties may beprovided by a manufacturer of the washer 24. The properties may alsoinclude a number of washers 24 that may be inserted in series on thefastener 23.

At block 84, the computing device may determine a spring rate (kbw) forthe series of washers 24 based on the properties received at block 82.The spring rate (kbw) may correspond to an amount of force provided whendeflecting the series of alternating washers 24 one inch. In oneembodiment, the spring rate (kbw) for the series of alternating washersmay be determined according to Equation 1 below:

$\begin{matrix}{k_{bw} = \frac{{maximum}\mspace{14mu}{washer}\mspace{14mu}{compression}\mspace{14mu}{force}}{{maximum}\mspace{14mu}{washer}\mspace{14mu}{deflection}*{number}\mspace{14mu}{of}\mspace{14mu}{washer}\mspace{14mu}{in}\mspace{14mu}{series}}} & (1)\end{matrix}$

At block 86, the computing device may calculate an axial force (f_(t))applied on the heat sink-semiconductor assembly 10 based on a torquevalue applied to the fastener 23. The torque value applied to thefastener 23 may correspond to a torque value specified by themanufacturer of the semiconductor device 14 or the heat sink 12. In oneembodiment, the axial force (f_(t)) applied on the heatsink-semiconductor assembly 10 may be determined according to Equation 2below:

$\begin{matrix}{f_{t} = \frac{Torque}{K \times {fastener}\mspace{14mu}{diameter}}} & (2)\end{matrix}$where Torque is the torque value specified by the manufacturer of thesemiconductor device 14 or the heat sink 12 for the heatsink-semiconductor assembly 10, K is a nut factor that is based on thematerials, plating, and lubrication of the internal and external threadsfor the fastener 23, and fastener diameter is a diameter of a part ofthe fastener 23 in which the washers 24 may be inserted.

At block 88, the computing device may calculate a deflection of theseries of the washers 24 after the fastener 23 is torqued at the torquevalue specified by the manufacturer. The deflection of the series ofwashers 24 may correspond to a distance in which the series of washers24 may compress after the fastener 23 is torqued at the torque value. Inone embodiment, the deflection of the series of the washers 24 may bedetermined according to Equation 3 below:

$\begin{matrix}{\delta = \frac{f_{t}}{k_{bw}}} & (3)\end{matrix}$

At block 90, the computing device may determine a percentage of residualforce remaining after the TIM 19 flows. In one embodiment, thepercentage of residual force may be determined according to Equation 4below:

$\begin{matrix}{{{Percentage}\mspace{14mu}{of}\mspace{14mu}{residual}\mspace{14mu}{force}} = {\frac{\delta - {{Expected}\mspace{14mu}{Change}\mspace{14mu}{in}\mspace{14mu}{Thickness}}}{\delta}*100}} & (4)\end{matrix}$

The Expected Change in Thickness corresponds to an expected change inthickness of the TIM 19 due to the heating of the heatsink-semiconductor assembly 10 during the manufacturing process or theburn-in process. The Expected Change in Thickness may be up to a 25%decrease in thickness.

Certain factors may be evaluated when determining the Expected Change inThickness. For example, the surface roughness of the both thesemiconductor device 14 and the heat sink 12 and the amount of the TIM19 may fill in the small crevices in these surfaces may be one factor indetermining the Expected Change in Thickness. A second factor may berelated to the flatness of the semiconductor device 14 and the heat sink12. If one or both of the semiconductor device 14 and the heat sink 12are concave, the TIM 19 may flow into a cupped area of the concavecurve. If one or both of the semiconductor device 14 and the heat sink12 are convex, the TIM 19 may more readily flow towards the edges andout from under the semiconductor device 14. A third factor may berelated to the amount of perimeter of the semiconductor device 14 ascompared to the total area of the semiconductor device 14. This ratiomay be related to an amount of the TIM 19 that may flow out of the edgesduring the burn-in process.

At block 92, the computing device may determine whether the percentageof the residual force determined at block 80 is greater than someassigned threshold value. The assigned threshold value may correspond toan acceptable percentage of force lost due to the TIM 19 flow. In oneembodiment, the assigned threshold value may be between 20% and 30% offorce lost or between 70% and 80% of the initial force maintained.

If, at block 92, the computing device determines that the percentage ofthe residual force determined at block 90 is not greater than theassigned threshold value, the computing device may return to block 82.After the computing device returns to block 82, the computing device mayrepeat the method 80 using washer properties for a different washer typeor a different number of washers for the same washer type.

If however, at block 92, the computing device determines that thepercentage of the residual force determined at block 90 is greater thanthe assigned threshold value, the computing device may proceed to block94. At block 94, the computing device may determine that the type ofwasher 24 and the number of washers 24 that corresponds to the washerproperties received at block 82 may adequately compensate for the lossof pressure or axial force between the heat sink 12 and thesemiconductor device 14 due to the TIM 19 flow.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

The invention claimed is:
 1. A system, comprising: a heat sink; asemiconductor device; a thermal interface material (TIM) disposedbetween the heat sink and the semiconductor device, wherein the TIM isconfigured to facilitate dissipation of heat generated by thesemiconductor device via the heat sink during operation of thesemiconductor device; and a fastener system that couples thesemiconductor device, the TIM, and the heat sink together, wherein thefastener system comprises a first Belleville-type washer and a secondBelleville-type washer, wherein the first Belleville-type washer and thesecond Belleville-type washer are arranged in series with each other,wherein each of the first and the second Belleville-type washer is in areverse position with respect to an adjacent Belleville-type washer. 2.The system of claim 1, wherein each of the first and secondBelleville-type washers includes a first side and a second side, whereinthe first side has a larger diameter than the second side.
 3. The systemof claim 2, wherein the first side of the first Belleville-type washeris positioned against a head of a fastener of the fastener system, andwherein the second side of the second Belleville-type washer ispositioned against the second side of the first Belleville-type washer.4. The system of claim 1, wherein the fastener system comprises a numberof Belleville-type washers corresponding to a size of a fastener of thefastener system, an amount of torque being applied to the fastener, anamount of expected deflection between the heat sink and thesemiconductor device after the TIM flows, or a combination thereof. 5.The system of claim 1, wherein the fastener system is configured tomaintain a coupling force between the semiconductor device and the heatsink after the TIM flows by providing a spring force configured to limita loss of an axial force between the heat sink and the semiconductordevice, wherein the axial force corresponds to a torque value applied toa fastener of the fastener system.
 6. The system of claim 5, wherein thecoupling force corresponds to a percentage of the axial force betweenthe heat sink and the semiconductor device when the fastener of thefastener system is torqued to a torque value associated with thesemiconductor device.
 7. The system of claim 6, wherein the percentageis between 70% and 80%.
 8. An industrial automation drive, comprising: aheat sink-semiconductor assembly comprising: a thermal interfacematerial (TIM) disposed between a semiconductor device and a heat sink,wherein the TIM is configured to facilitate dissipation of heatgenerated by the semiconductor device via the heat sink during operationof the semiconductor device, and wherein the semiconductor device isconfigured to convert an alternating current (AC) voltage into a directcurrent (DC) voltage or convert the DC voltage into a controllable ACvoltage; and a fastener system, comprising: a fastener configured tocouple the semiconductor device to the heat sink about the TIM; and afirst and a second Belleville-type washer configured to maintain asubstantially constant coupling force between the semiconductor deviceand the heat sink about the TIM during operation of the semiconductordevice, wherein the TIM flows when heated beyond a thresholdtemperature, wherein the first Belleville-type washer and the secondBelleville-type washer are arranged in series with each other, whereineach of the first and the second Belleville-type washer is in a reverseposition with respect to an adjacent Belleville-type washer.
 9. Theindustrial automation drive of claim 8, wherein the coupling forcecorresponds to a percentage of an axial force applied between the heatsink and the semiconductor device, wherein the axial force is associatedwith a torque value applied to the fastener before the TIM flows. 10.The industrial automation drive of claim 9, wherein the percentage isbetween 70% and 80%.
 11. The industrial automation drive of claim 8,wherein the fastener system comprises a number of Belleville-typewashers corresponding to a size of the fastener of the fastener system,an amount of torque being applied to the fastener, and an amount ofexpected deflection between the heat sink and the semiconductor deviceafter the TIM flows.
 12. The industrial automation drive of claim 8,wherein each of the first and second Belleville-type washers includes afirst side and a second side, and wherein the first side has a largerdiameter than the second side.
 13. The industrial automation drive ofclaim 12, wherein the first side of the first Belleville-type washer ispositioned against a head of the fastener, and wherein the second sideof the second Belleville-type washer is positioned against the secondside of the first Belleville-type washer.
 14. A fastener system,comprising: a fastener configured to couple a semiconductor device, athermal interface material (TIM), and a heat sink together; and a firstand a second Belleville-type washer configured to maintain asubstantially constant coupling force between the semiconductor deviceand the heat sink during operation of the semiconductor device with theTIM disposed between the semiconductor device and the heat sink, whereinthe first Belleville-type washer and the second Belleville-type washerare arranged in series with each other, wherein each of the first andthe second Belleville-type washer is in a reverse position with respectto an adjacent Belleville-type washer.
 15. The fastener system of claim14, wherein each of the first and the second Belleville-type washersincludes a first side and a second side, wherein the first side has alarger diameter than the second side.
 16. The fastener system of claim15, wherein the first side of the first Belleville-type washer ispositioned against a head of the fastener, and wherein the second sideof the second Belleville-type washer is positioned against the secondside of the first Belleville-type washer.
 17. The fastener system ofclaim 14, comprising a number of Belleville-type washers correspondingto a size of the fastener, an amount of torque being applied to thefastener, an amount of expected deflection between the heat sink and thesemiconductor device after the TIM flows, or a combination thereof. 18.The fastener system of claim 14, wherein the first Belleville-typewasher is configured to maintain the coupling force between thesemiconductor device and the heat sink after the TIM flows by providinga spring force, wherein the spring force is configured to limit a lossof an axial force between the heat sink and the semiconductor device,wherein the axial force corresponds to a torque value applied to thefastener.